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Science

Breeding for dry climates: Some plants like it hot

Member states to the United Nations convention on desertification are meeting in Cancun to discuss what can be done to stop soil degradation. One possibility is crops bred to withstand drought.

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Peru's potato varieties

Extended periods of drought can destroy not only harvests - at the edges of savannahs or near deserts, they can destroy all human livelihood. As farming becomes impossible, people turn to pastoralism, or letting cattle or goats browse natural vegetation off the land. The result: The animals eat what is left of any plants, allowing the wind and rain remove the remaining topsoil, and letting desertification continue its march forward.

This problem could be addressed with crops that are able to survive a dry spell and still produce yields, even under difficult conditions. This would help to protect and possibly even improve the soil - preventing a dry spell from becoming a disastrous drought.

Some wild varieties more resistant

Farmers struggling with dry climates need plants that are able to survive on little water. And it is possible to breed such crops, because there are enough varieties of wild plants that can survive dry spells. However, such sturdy varieties do not typically make good crops.

"In all sorts of plants around the world, you will find large variety - both within wild forms, and within domesticated or bred forms," says Jens Leon, a professor of plant breeding at the agriculture faculty at Bonn University.

"That's why it's interesting to look out for new genotypes - meaning forms that have specific genetic capabilities - and that are able to cope with challenges like droughts better than others can."

Leon and his colleagues all over the world are trying to cross-breed crops with robust wild varieties to produce highly productive domesticated plants. They hope to get crops that can both survive a dry spell, and deliver high yield. They are working to identify specific genetic mechanisms in the plants.

"We try to learn about the mechanisms and pinpoint them with DNA markers, or specific sections of the DNA that we can research very well," Leon explains. "Then we try to find out what relationship exists between these markers and the specific qualities of the plant."

Once the biologists have identified their candidates, the real work begins. "We identify parent plants in a classical way, for example we know of some that are resistant to salt. Those we cross-breed with other parents that are delivering high yield," Leon says.

Students at the Max-Planck-Institut for Molecular Plant Physiology (Photo: Picture Alliance/dpa)

Successful plant breeding requires time and effort: Tens of thousands of lines have to be bred and compared

Perseverance pays off

In practice, this work requires untold patience and diligence. It is not always clear what triggers better or worse development of a specific plant line. Heiner Goldbach, a professor for plant nutrition at the Bonn University, says differences in the soil structure can make plant breeding tricky.

"A breeder may grow 10,000 varieties assuming that his soil is homogenous. But in most cases, it is not," Goldbach told DW. Despite soil that looks smooth and homogenous, in reality there could be highly diverse patches of soil, he says.

Researchers must therefore introduce as many factors as possible into their analysis. "Sensors can help make the observations of the breeders more objective," Goldbach says. The qualities of the plant must be observed - "which a breeder cannot see with his eyes only - for example, processes that take place within photosynthesis."

Many different factors, one big picture

Such a process can be observed through examining the chlorophyll content of the leaves. Sensors can also detect the impact of parasites, or effects of fertilization and nutrient supply. To get the most complete picture, the breeders need data from as many sensors as possible.

"Each sensor has its advantages and disadvantages," Goldbach points out. "Some things it can see, others it can't. We like to find combinations that deliver us the most useful information."

That's why the scientists overlay the results from several sensors. The resulting grid is called sensor integration. Through this process, many factors that are responsible for how the plant grows can be identified.

In the end, every new bred line must prove itself in real life: Only in the field will it be possible to see if the crop survives several weeks or months without water, or in other difficult weather conditions. And that could decide whether farmers are able to continue to work their land.

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